Often one of the most important features of a product is its appearance. Automobile manufacturers are particularly concerned with the appearance of the automobiles they manufacture. Components such as, for example, automobile body panels, trim components, side view mirror housings and similar automobile parts have traditionally been spray painted to provide a desired appearance (i.e., color and finish). Recently, the spray painting of certain exterior automobile parts has been replaced with a prefabricated multi-layer paint film. In addition to other advantages, such paint films avoid the environmental problems associated with evaporating paint solvents and eliminate the need for additional paint facilities and the associated equipment, ovens, sludge disposal, and emission control systems. However, the use of prior paint films has had mixed results, particularly with regard to color and surface finish.
Such paint films typically include a decorative layer having the desired paint finish and are often pre-formed such as by thermoforming (i.e., forming the film while in a heated state). The pre-formed paint film is then adhered to the desired surface(s) of the part. When it is a plastic molded part, paint films have been adhered by being insert molded with the part. The decorative layer of some paint films have been formed by being cast onto a carrier layer. The surface of the carrier layer, on which the decorative layer is cast, is formed so as to produce the surface finish desired on the decorative layer. In addition, it has been taught to leave the carrier layer on the paint film, after the paint film is manufactured, to protect the paint film during shipping and handling and during subsequent application of the film to the part (e.g., thermoforming the paint film into a pre-formed state for bonding to the part).
Automobile manufacturers often require that the painted surfaces on their automobiles exhibit a very high gloss and DOI (i.e., Distinctness Of Image or mirror-like reflection), especially for metallic paint finishes. Casting the decorative layer onto a carrier layer having a high gloss finish has resulted in paint films with a high gloss and DOI. However, the thermoformability of some prior carrier layers has been very limited, thereby limiting the uses of the paint films to flat or lightly contoured parts. Paint films with carrier layers that exhibit improved thermoformability can be found, such as those described in U.S. Pat. No. 5,215,826 to Shimanski et al. However, the thermoformability of these carrier layers is still too limited. In addition, even with prior carrier layers that exhibit sufficient thermoformability for a particular use, too often a significant reduction in the gloss and DOI of the paint film has been observed after the paint film and carrier layer have been thermoformed.
Therefore, there is a need for a better way to protect a paint film during shipping and handling and during subsequent application of the film to the part (e.g., thermoforming the paint film into a pre-formed state for bonding to the part) while substantially retaining the surface finish of the paint film, particularly the gloss and DOI.